From the Guidelines
Oral hydralazine should be initiated at a dose of 25 mg three times daily and titrated upward to the maximum dose as needed. This dosing strategy is based on the recommendations from the American Heart Association for the management of resistant hypertension, as outlined in the 2018 scientific statement published in the journal Hypertension 1. The dose can be adjusted based on the patient's response, with a maximum dose not explicitly stated in the provided evidence but typically ranging from 25 to 100 mg four times daily in clinical practice.
When considering the use of hydralazine, especially in patients with congestive heart failure with reduced ejection fraction, it is crucial to administer it on a background of isosorbide mononitrate 30 mg daily, with a maximum dose of 90 mg daily, as suggested by the same guidelines 1. This combination is aimed at optimizing the management of resistant hypertension while considering the patient's overall cardiovascular health.
Key points to consider in the dosing of oral hydralazine include:
- Starting dose: 25 mg three times daily
- Titration: Upward as needed to achieve blood pressure control
- Background therapy for patients with congestive heart failure with reduced ejection fraction: Isosorbide mononitrate 30 mg daily (max dose 90 mg daily)
- Monitoring parameters: Blood pressure response, heart rate, signs of fluid retention, and symptoms of lupus-like syndrome, particularly with higher doses or in slow acetylators.
The mechanism of action of hydralazine as a direct vasodilator, leading to decreased peripheral resistance and blood pressure reduction, supports its use in combination with other antihypertensive agents to manage potential side effects such as reflex tachycardia and fluid retention. Consistent administration with respect to meals is recommended, as food can affect the absorption of hydralazine. The effects of hydralazine begin within 20-30 minutes of oral administration, peak at 1-2 hours, and last 6-8 hours, which necessitates a multiple daily dosing schedule.
From the FDA Drug Label
DOSAGE AND ADMINISTRATION Initiate therapy in gradually increasing dosages; adjust according to individual response. Start with 10 mg four times daily for the first 2 to 4 days, increase to 25 mg four times daily for the balance of the first week. For the second and subsequent weeks, increase dosage to 50 mg four times daily. For maintenance, adjust dosage to the lowest effective levels. In a few resistant patients, up to 300 mg of hydrALAZINE hydrochloride tablets daily may be required for a significant antihypertensive effect.
The dosing of oral hydralazine is as follows:
- Initial dose: 10 mg four times daily for the first 2 to 4 days
- First week: 25 mg four times daily
- Second and subsequent weeks: 50 mg four times daily
- Maintenance dose: adjust to the lowest effective level
- Maximum dose: up to 300 mg daily in resistant patients 2
From the Research
Dosing of Oral Hydralazine
- The dosing of oral hydralazine is not explicitly stated in the provided studies as a primary focus, but it can be inferred from the contexts in which hydralazine is mentioned, particularly in combination with other medications for the treatment of heart failure.
- In the study 3, hydralazine doses ranged from 25 to 150 mg orally, which is equivalent to 0.37 to 2.86 mg/kg, indicating a potential dosage range for oral administration.
- The effects of hydralazine on blood pressure, cardiac output, and peripheral resistance were observed with respect to dose, age, and acetylator status in this study, suggesting that dosing may need to be considered in the context of individual patient factors.
- However, the primary studies 4, 5 discuss the use of hydralazine in combination with nitrates for heart failure treatment rather than focusing on the dosing of oral hydralazine itself.
- These studies highlight the efficacy of the hydralazine and nitrate combination in certain patient populations, such as African-American patients with heart failure, but do not provide detailed information on the optimal dosing of oral hydralazine.